The one-dimensional conformal model and the three-dimensional model for phase-resolving numerical simulation of sea waves were used for investigation of a freak wave nature. The calculations with conformal model were done for 7120 peak wave periods. The small subgrid dissipation of energy was compensated by integral input of energy, so, the energy was preserved with the accuracy of 4 decimal digits. The probability of the trough-to-crest wave height, crest wave height and trough depth were calculated. The uncertainty (dispersion) of the calculated probability is demonstrated. It is confirmed that trough-to-crest height equal to 2, approximately corresponds to the crest height equal to 1.2. Freak waves appear randomly in a form of the groups separated with large intervals of time. The hypothesis that freak wave can appear as a superposition of modes gathering in the vicinity of a dominant wave crest turned out to be incorrect. It was proved by a special phase analysis with the conformal model and 2D-model that the height of wave does not correlate with the phase concentration (expressed as a sum of crest heights of modes in the vicinity of crest of the main mode). The probability of large waves is monotonic over the wave height. It allows us to suggest that large waves are an indigenous property of a random wave field, and they are typical though quite rare events. The spectral image of wave field with a small number of modes can indicate the presence of freak waves, but this effect disappears completely when the length of such wave is much smaller than the size of domain. The Fourier approximation of freak wave in such domain requires many spectral modes in the same way as the approximation of pulse function. The abnormal growth of wave height looks rather like the self-focusing of single wave involving concentration of energy in the vicinity of wave peak. The breathers most closely correspond to the nature of freak waves.

On an idealized 2D-cross-section of the continental slope, the situation in the polar regions is simulated — dense water falls to the seafloor from the continental shelf. On the solutions of two problems in the hydrostatic approximation and in the complete nonhydrostatic formulation, the dynamic characteristics of the process are compared: the fields of velocity, pressure, motion and the structure of the dense lens of water. The same comparison is carried out on the solution of the model problem of gravitational adaptation to equilibrium — an immanent line of dynamics on the continental slope. Based on the results of 3D-modelling of the dynamics and hydrology of the Lombok Strait (Indonesian Archipelago), the fields of hydrostatic and nonhydrostatic vertical velocity are compared at the slope of the strait. The simulation result of the vertical velocity and its spectra in the tidal cycle of the M₂ wave are presented. The comparison shows the inadequacy of modelling slope dynamics in the hydrostatic approximation.

The introductory overview is prepared for the planning interdisciplinary research (from positions of oceanography, hydrobiology, ecological and experimental physiology, materials science) on the problem of biofouling in sense of systematizing the knowledge and development of approaches to monitoring of the phenomenon; carrying out actual natural observations and experiments aimed to reveal patterns of formation of fouling community in conditions of different types of technogenically transformed and artificial ecosystems under impact of diverse driving forces.
The overview evaluates the modern state of knowledge required for implementation long-lasting preventative programs directed to solution of biohazards’ problem on the example of an energy asset as well as perspectives in use of fouling organisms as objects of biotechnologies for water quality improvement in transformed or(and) aquatic territories adjacent to urbanized regions.
The communication is finished with background sketch for development of a model project of targeted scientific research and experimental design works expected to be implemented in the frame of the National Projects of the Russian Federation and within international cooperation programs in the Baltic Sea region.

To determine baroclinic tidal energy dissipation and its related diapycnal diffusivity, we have used a high-resolution version of the 3D finite-element hydrostatic model QUODDY-4, equipped with an indirect means for describing tidal effects. The latters are parameterized in the terms of a corrected (with account for diapycnal diffusion) vertical eddy diffusivity. A diapycnal diffusivity is found from the solution of an auxiliary task on dynamics of internal tidal waves (ITWs). The derived solution shows that the vertical eddy and diapycnal diffusivities have nearby orders of magnitude, that the fields of climatic characteristics in the sea are subjected to quite marked changes due to ITW-induced diapycnal diffusion and that, hence, the conclusion obtained early, concerning an important role of tidal effects in the formation of regional climates of the Barents and Kara Seas remains valid for the Laptev Sea as well.

The following article provides the research on interannual temperature oscillations of the Barents Sea and the Kara Sea based on mode results only without using the reanalysis data in the water temperature distribution during the 1 to 12-year period. Model solution of 1975–2005 received according to the two different spatial resolution model data are used for the following research. The correct representation of the researched area climate by these models is determined. Interannual water temperature oscillations amplitude magnitude may be compared to the ones of the interseasonal oscillations in the researched area. The wavelet analysis method, providing the opportunity for the research of the periodical components despite their frequency changes, is used here to detect the periodicity and possible frequency instability. The analysis results demonstrate that the atmosphere temperature oscillations and ice cover area oscillations show the similar periods. It’s worth mentioning that some of the known oscillations in the Ocean-Atmosphere system match the oscillations intervals received according to model results. In the atmosphere temperature and the water temperature oscillation of the initial data distribution the connection between the oscillations range and the ice edge position can be followed clearly. In the water and air temperature oscillations in the local points the 3 basic supporting frequencies of the presented parameters are distinguished. They correspond to the 1.0–3.6 year, 3.9–5.8 year, 6.3–10.5 year periods as well as to the basic supporting oscillation periods at the “Kola meridian” stations. Ice cover area oscillation ranges are fully contained in the stated ranges of the 3 basic water and air temperature oscillations in the researched local points of the Barents Sea and the Kara Sea. The sea oscillation intensity depends on the ice edge position and is presented mostly in the areas which are covered by the snow during the less period of time. Two-dimensional distribution of the temperature oscillation amplitudes demonstrates that the high-frequent oscillations (periods lasting up to 4.1 year) get the more evident vision on the surface and are poorly presented in the low layers. On the contrary the long period (lasting more than 8 years) oscillations appear nearly everywhere. In the low layers such oscillations can spread especially wide including the distance up to the north end of the researched area.

In this article, based on the analysis of the results of contact and satellite observations made in August 2016 in the coastal zone of the Barents Sea, the characteristics of short-period internal waves and features of their manifestations on the surface in radar data are estimated. According to a series of rapid CTD probes, 270 internal waves with an average period of about 15 minutes and a height of 1 to 8 meters were registered. It is shown that the intensification of internal waves occurs mainly at low tide: against the background of a relatively calm pycnocline, pronounced train wave systems appear. Satellite images showed 82 packets of internal wave manifestations, with an average of 4 waves per packet. As a rule, the length of the leading ridge in the package was 27 kilometers, and the wave length was 700 meters. The common geometrical characteristics in the manifestations of waves in the areas of distribution, they were divided into two groups: the first was observed on the removal of 40–100 kilometers from the coast with direction North-West along the coast, the second spread from the coast to the North. A possible source of generation of two groups of waves is interaction between tide and unevenness of the bottom topography. The wavelengths and phase velocities are very close according to contact and satellite observations. Direct comparison of data from contact and satellite observations showed that internal waves with an amplitude of 2.5–4 meters are reflected in satellite observations at a depth of pycnocline of about 15 meters.

The change of thermobaric regime of the hydrate-bearing sediment layer caused by an increase in the near bottom water’s temperature in Lake Baikal during the Holocene is investigated by solving the methane hydrate — free gas + water phase transition problem. It was demonstrated that the gas released during the methane hydrates dissociation does not create an abnormal pore pressure and efficiently migrates out from the decomposition zone provided that the primary permeability value of the porous medium is typical for the upper layers of the sedimentary cover in Lake Baikal. The phase transition problem becomes a purely thermal one. Its numerical solution makes it easy to estimate the phase boundary displacement with increasing water temperature in the lake, and hence the mass of free gas released from the hydrate. The specific mass of the released gas per unit area of the lake ranges from 50 to 110 kg/m², as shown by the results of such a numerical solution using data on both the lake’s depth and the hydrate-bearing layer thickness obtained from many points in the Southern and Central Basins of the lake. The minimum values correspond to the maximum water depths at the same time with the maximum thicknesses of the hydrate-bearing layer. On the contrary, the maximum values correspond to minima. Distribution maps of gas mass have been constructed. The total amount of methane released in the Holocene from gas hydrates is estimated at approximately 500 million tons (about 800 billion cubic meters under normal surface conditions). This value is obtained by integrating the calculated masses over the area of two regions in the Southern and Central Basins and subsequent extrapolation of the results to the entire their water area (there are no gas hydrates in the sediments of the Northern Basin).

The article shows a mathematical model to study the characteristics and mechanisms of formation of wave and vortex structures formed by the flow around the obstacle at the scales corresponding to submesoscale phenomena in natural conditions. The problem of flow around a barrier in the form of a hemisphere with a diameter of 20 m with a base at the bottom of a two-layer laminar flow of a viscous incompressible liquid is solved. The vortex dynamics of the flow behind the barrier was resolved explicitly using the hybrid method of detached eddies. Based on numerical experiments, it is shown that in the studied range of Froude number 0.0017–0.0272 the flow process is non-stationary with the formation of coherent vortex structures that grow over time and down the stream to the characteristic scales of the obstacle, and then transfer energy to the wave components.

Ultra-wide-band observing systems have not yet been created. However, theoretical advantages of sonar systems adapting to changes of hydrophysical conditions seem to be clearly visible in the study of marine mammalian sonar. Therefore, technical equipment for a broadband recording system under long-term laboratory experience is necessary. It makes possible studying the mobile broadband sonar using accurate biophysical and appropriate techniques that limiting the animal’s mobility during echolocation. The paper provides a number of methodological solutions for conducting an experiment on dolphins, which makes possible studying the noise immunity and secrecy of a natural sonar, and subsequently conduct comparative tests with technical analogues. Based on the presented methods, comparative estimates of echolocation signals belonging to various species of marine mammals will be obtained, and a database of biological signals will be formed — the search, tracking and recognition of underwater objects in difficult conditions of natural and artificial acoustic noise.